Plotting instrument



Y- L. WERNSTEDT PLOTTING INSTRUMENT Filed May-29, 1941 7 Sheets-Sheet l INVENTOR L'AGE WERNSTEDT ATTORNEYS 1942- L. WERNSTEDT PLOTTING INSTRUMENT Filed May 29, 1941 '7 Sheets-Sheet 2 INVENTOR LAGE WERNSTEDT ATTORNEYS Nov. 24, 1942. L WERNSTEDT 2,303,099

PLOTTING INSTRUMENT Filed May 29,. 1941 7 Sheets-Sheet 3 INVENTOR LAGE WERNSTEDT ATTORNEYS Nov. 24, 1942. 1.. WERNSTEDT PLOTTING INSTRUMENT Filed May 29, 1941 7 Sheets-Sheet 4 1942' 1.. WERNSTEDT PLOTTING INSTRUMENT Filed May 29, 1941 '7 Sheets-Sheet 6 m m E E WT N N W E T v T NE A I Q Nov. 24, 1942- L. WERNSTEDT PLOTTING- INSTRUMENT 7 Sheets-Sheet 7 Filed May 29, 1941 Iii O -lNVENTO| LAGE WERNST-EDT ATTORNEYS Patented Nov. 24. 1942 UNITED STATES PATENT OFFICE PLOTTING INSTRUMENT Lage Wernstedt, Portland, Oreg. Application May 29, 1941, Serial No. 395,736

8 Claims. (01. 33-20) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed, if patented, may be manufactured and used by or for the Government of the United states of America for governmental purposes without the payment to me of any royaltythereon.

This invention relates to photogrammetry generally and the principal object is the provision of an instrument in which a pair of vertical photographs having a stereoscopic overlap can be viewed stereoscopically and maps fabricated giving the topography and planimetry of observed relief images. Such devices are generally referred to as stereoscopic plotting instruments.

The nature of vertical photographs taken of uneven terrain is that objects closer to the camera are on a larger scale than those farther away. Another object of this invention is the provision of an instrument by means of which a topographic map of uniform scale can be made from such pictures notwithstanding such scale variations in each picture.

The following description, considered together with the accompanying drawings, will more fully disclose this invention and further objects and advantages thereof will be apparent;

In the drawings: I

Figure 1 is a front elevational view illustrating the general arrangement of parts of an embodiment of my invention, partly broken away.

Figure 2 is a partial top plan view.

'Figure 3 is a plan view showing one of the index marks and the means of supporting it on its guide bar, said bar being shown fragmentarily.

Figure 4 is a section along the line 4-4 of Figure 1.

Figure 5 is a section along the line 5-5 of Figure 1.

Figure 6 is a section along the line 66 of Figure 5.

Figure 7 is an enlarged section along the line of Figure 6. I

Figure 8 is an enlarged section along the line 8-8 of Figure 6.

Figure 9 is a section along the line 9- -9 of Figure '7.

Figure 10 is an enlarged front elevational view of one of the phototables, partly in section.

Figure 11 is a fragmentary plan view along the line! l-ll of Figure 1. K

Figure 12 is an enlarged fragmentary view illustrating the means for holding the runners BI and 82 in position.

Figure 13 is a partial l3l3 of Figure 1.

Figure 14 1s a fragmentary plan view along the line l4-I4 of Figure 13.

Figure 15 is a fragmentary view taken along the line I5--l5 of Figure 13.

Figure 16 is an enlarged section along the line lG-li of Figure 13.

Figure .17 is a section along the line |I--l| of Figure 1. The broken lines shown illustrate the relative position of parts when the floating mark carriage is moved forward.

Figure 18 is an enlarged fragmentary view illustrating the tracing point assembly as viewed in Figure 1.

Figure 19 is an enlarged fragmentary view of Figure 1 showing in detail the wheel scale IOI and pointer I 03.

section along the line Figure 20 is a section along the line 2020- of Figure 19.

Figure 21 isa section along the line 2|--2l of Figure 10.

Referring with more particularity to the drawings in which like numerals designate like parts, the embodiment illustrated is mounted on a suittable working table 25 over which is disposed a stereoscope consisting of a pair of horizontal eyepieces 28 and 21 beneath which are mounted the usual eye mirrors 28 and 29.- These mirrors may be either plane-surfaced mirrors or prisms.

The drawings illustrate them as plane-surfaced,

mirrors which are preferably of first surface reflection. The eyepieces 26 and 21 and mirrors 28 and 29 are co-mounted on a frame 30 which is horizontally pivoted to the vertical arm 3| of an angle bracket 32 and held in adjusted positions by means of a clamping bolt 33. The horizontal arm 34 of said bracket is vertically pivoted to a carriage 3'5 and held in adjusted positions by means of a clamping bolt 36. The carriage 35 carries horizontal sleeves 31 and 38 which are co-slidable on parallel front and rear bars 39 and 40, respectively. The bars 39 and 40 are fixed to the arms 4| and 42 ofupright supports 43 and 44, respectively. The uprights 43 and 44 are fixed to the table 25 as shown. The slidable relation of the carriage 35 on the bars 39 and 40 is controlled by a shaft 45 threaded at one end to engage a threaded aperture 46 of the carriage 35, the other end being rotatably supported in a suitable bearing 4] on the arm 42. This end of the shaft 45 extends through the bearing 41 to which is secured a hand wheel 48 for manually imparting rotation to said shaft.

On the forward bar 39, the wing mirrors 49 and 58 of the stereoscope are mounted. These wing mirrors are held in frames 5| and 52 which are pivoted to the vertical arms 53 and 54 of angle brackets 55 and 58. The horizontal arms 51 and 58 of said brackets are pivoted to sleeves 58 and 88, which sleeves are slidable on the said bar 38. Arms 8| and 82 are fixed to sleeves 58 and 88 and are provided with horizontal slots 83 and 84 engaging the stem of vertical head screws 85 and 88, mounted on the arms 4| and 42. Adjusted positions of the sleeves 58 and 88 are set by means of abutment screws 81 and 88 mounted through the arms 4| and 42 to abut the outer sides of the sleeves 58 and 88. By these means, adjustments of the mirrors 48 and 58 in the horizontal direction along the bar 38 are permitted within the limits of the slots 83 and 84 by changing the positions of the abutment screws 81 and 88 and a levelling adjustment is obtained by changing the position of screws 85 and 88. The mirrors 48 and 58 can also be pivoted horizontally and vertically by means of the pivoted connections with the brackets 55 and 58 to bring them parallel to the eyepiece mirrors 28 and 28.

Beneath the wing mirrors 48 and 58, phototables 88 and 18 are mounted on the table 25 for supporting the steroscopic pictures. Each table comprises a platen 1| rotatable on a vertical shaft 12 fixed to the center of a disc 13. The disc 13 is provided with a curved slot 14 through which an arcuated rack 15 is disposed, said rack being fixed to the bottom of the platen 1|. A shaft 18, rotatable in bearings 11 and 18 on the bottom of the disc 13, carries a worm 18 engaging said rack 15. This shaft 18 extends outward to the front of the table 25 and is provided with a knob 88 for manually imparting rotation.

To the bottom of the disc 13 there are fixed a pair of circular runners 8| and 82, the center of curvature of which will be defined hereinafter. These runners are supported and slide on the top edge of vertical plates 83 and 84 which are secured to a horizontal plate 85 extending between the runners 8| and 82.

Between the runners 8| and 82 there is fixed to the bottom of the disc 13 a rack 88 having a curvature parallel to the curvature of said runners. The rack 88 engages a worm 81 which is fixed to a shaft 88. The shaft 88 is rotatably mounted in a bearing 88 which is secured to the bottom of the plate 85 and a bearing 88 through the vertical plate 84. The shaft 88 extends to the front of the instrument where it is provided with a knob 8| for imparting manual rotation. The runners 8| and 82 are held against the vertical plates 83 and 84 by means of curved slots 82 and 83 through the runners Hand 82 engaging pins 84 and 85 projecting laterally from the plate 85. The bottoms of the vertical plates 83 and 84 are cut 88 and 81 which slide in complementary concave bearing surfaces 88 and 88 on top of vertical plates I88 and Ill. The plates I88 and I8I are fixed to a horizontal plate I82 by means of angle braces I83 and I84, said plate I82 being secured to the top of a vertical post I85. To the outer sides of the vertical plates 83 and 84 racks I88 and I81.are secured, said racks having a curve.- ture concentric with the runners 88 and 81. Pinions I88 and I88 mesh with the racks I88 and I81 and are fixed to a common shaft II8 rotatably mounted in bearings III and H2, said bearings being fixed'to the bottom of the horizontal plate I82. The shaft 8 extends to the to form circular convex runners front of the table 25 and is provided with a knob II3 for imparting manual rotation. The racks I88 and I81 are held In contact with the pinions I88 and I88, and the runners 88 and 81 are held engaged with the bearing surfaces 88 and 88 by means of arm hooks I I4 and H5, one end of each of which is fixed to the bottom of plate I82 from which they extend outward underthe racks I88 and I81, thence upward, and thence inward to bear upon shoulders H8 and 1 of said racks I88 and I81.

The centers of curvature of the runners 8| and 82 and runners 88 and 81 are determined by trial and error to be the point about which a picture placed on the platen 1| should be turned to bring the visual rays of the stereoscope in coincidence with the corresponding horizontal and vertical position of the points of the optical model with the least error. These centers are preferably detiifiined graphically by constructing a diagram of the images of points representing a picture and their corresponding positions in the spatial model, thence, determining the position of the picture points which will bring the rays from the stereoscope in coincidence with the corresponding points of the model with the least error. The point about which the picture points should swing to obtain this condition is the center of curvature in each case and the distance of the runners 8| and 82, and 88 and 81 from this center determines their radii. The center of curvature in each case, i. e., for both the runners 8| and 82 and the runners 88 and 81, will be at the same vertical distance above the platen 1 I.

The post I85 is mounted through a horizontal plate H8 and is provided with a rack Ii8 engaging a pinion I28. The pinion I28 is fixed to one end of a shaft |2I the other end extending to the front of table 25 through a bearing I22 and a clamp I23. Said clamp is set and released by means of a screw I24, whereby the shaft I2| can be releasably held in different positions of rotation to prevent vertical movement of the phototable assembly after adjustment. The shaft I2| carries a knob I25 for manually imparting rotation when the clamp I23 is released.

The sides of the plate 8 are straight edges and are slidable between guides I28 and I21. These guides are laterally adjustable by means of slots I28 and I28 engaging hold down screws I38 and |3I on the table 25. A large opening I3IA is provided through table 25, through which the lower part of the post I85 projects, said opening being large enough to permit freedom of movement of said post when said plates are moved in diflerent positions within the limits of adjust-.

ments desired. I

Between the phototables 88 and 18 there is mounted the map table I32, upon which the map to be made is drawn. The map table I32 is fixed to a spherical bearing I33, the spherical surface of which is in slidable contact with the upper rim of a collar I34. The collar I34 is integral with the top of a hollow vertical tube I35, the bottom of which is closed except for an aperture I38 through which a rod I31 is axially disposed. The upper end of the rod I31 is fixed to a ball I38, said ball being disposed in a socket I38 integral with the map table I32. The lower end of the rod I31, extending through the aperture I38, is threaded to engage a nut I48, said nut I48 having a shank I which abuts the lower end of the tube I35. About the shank I, there is disposed a spring I42 between the flanged head I43 of the nut I48 and the bottom of the tube I35 for the purpose of applying a downward pressure a; ainst the nut I46. By tightening'the nut I 46, the table I62 is held in a fixed position and by loosening it the table is released from the fixed position and may be tilted and tipped. In this released position, spring I42 acts to create a drag to the movement of the table I62.

The tube I65 is mounted in a sleeve I44, which is disposed through an aperture I46 of the table 25. The collar I64 rests on top of said sleeve. The outer side of the sleeve I44 is threaded and engages a nut I45 fixed to the bottom of the table 25 by means of screws I46A, or any other suitable means. The sleeve I44 is provided with a knurled fiange I41 for manually rotating it to change the elevation of the sleeve together with the tube I65 and the map table I62. The map table I62 is leveled by loosening the nut I46, permitting it tobe tipped and tilted into a level position with the assistance of a level bubble (not shown), after which the nut I46 is tightened to increase the friction between the bearing I66 and the collar I64, sufiicient to prevent movement under the pressure of the tracing point, hereinafter described.

Between the phototables 66and 16 and the wing mirrors 46 and 56, index marks I46 and I46, etched or otherwise provided on thin transparent discs I56 and II of glass, or some other suitable material, are disposed. These marks are preferably of a color contrasting with the color or colors of the photographs to be used, and are mounted on a carriage as follows: The discs I56 and I5I are mounted in frames I52 and I56 which are supported vertically on beveled arms I54 .and I55. These beveled arms are vertically slidable in dovetailed grooves I56 and I51 of brackets I 56 and I56 with a friction fit and said brackets are fixed to sleeves I66 and I6! on a horizontal bar I62. The ends of bar I62 are fixed to vertical sleeves I63 and I64 which operate on racked vertical columns I 65 and I66. Mounted on said sleeves I 66 and I64 are pinions I61 and I66 engaging the racks I66 and I16 of said columns. These pinions are fixed to a shaft "I, one end of which is provided with a hand wheel I12, the rotation of which causes the sleeves I62 and I64 to move vertically on the columns I65 and I 66, together with the bar I62 and index marks I46 and I46 attached thereto. The bar I62, sleeves I66 and I6I, and parts movable therewith on the columns I65 and I66 are counter-balanced by means of counterweights I16 and I14 connected to the sleeves I66 and I6I by cables I15 and I16 operating over pulleys I11 and I16 on the top of columns I65 and I66. The counterweights I16 and I14 operate in vertical guide tubes I16 and I66 clamped or otherwise secured to the columns I65 and I66. Fixed to shaft "I is a wheel I6I having a graduated scale I62 on its rim. A pointer I66, fixed to the bar I62, extends in juxtaposition to the said scale I 62. By these means the index marks I46 and I46 can be set at any desired height.

The columns I65 and I66 are fixed to foot plates I64 and I65, which are rigidly secured to the ends of a stiff rod 266. Said foot plates are threadedly engaged with vertical posts I66 and I61, To each of-the posts I66 and I61 there is attached a foot I66 which slides over one of the plane surfaces I66 and I66, there being one of said surfaces for each of the columns I65 and I66.. The plane surfaces I66 and I66 are preferably of smooth plate glass, hard metal, or some other suitable material, to reduce friction. These 75 of surfaces are mounted on tables I 6| and I62, which tables are supported on levelling screws (preferably three'for each table) I66, I64, and I65, and I66, I61, and I66. Each foot I66 comprises ball bearings I66 disposed between the plane surface and a thrust collar 266 secured to the bottom of the foot, said ball bearings being held in position by a mounting 26I.

The index marks I46 and I 46 are maintained in lateral alignment, parallel to the base line or direction of correspondence of the stereoscopic pictures, by means of a suitable parallelism mechanism. The mechanism illustrated comprises two drafting machines 262 and 266 of a conventional type, one end of each of which is fixed to the table 25, the other end being hinged to one of the foot plates I64 and. I by meansof hinge pins 264 and 265, substantially asillustrated. Consequently, once the index marks are set their co-movement is constrained to positions parallel to every other position. I

On said rod 266 a bracket 261 is slidably mounted by means of a split sleeve 266 which may be tightened and loosened about the rod 266 by means of bolts 266 to clamp the bracket 261 in different positions along said rod 266. However, any other suitable clamping means may be provided. A forwardly extending arm. 2I6 projects from the bracket 261, to which arm there is secured a vertical sleeve 2 in which a vertical post 2I2 is slidably mounted- The lower end of the post 2I2 is provided with a tracing point, such as a pencil, pen, or other stylus, 2I6 adapted to contact the top surface of the map table I62. A weight 2 is mounted on the upper end of the post 2I2 resting on an abutment shoulder 2I5 for the purpose of applying pressure on the tracing point 2I3 against the map table I62; When not in use, the tracing point can be elevated out of contact with the map table I62 by means of a flexible cable 2I6 having one end fixed to the lower end of the post 2I2 and the other end to a ring 2I1 which may be slipped over a pin 2I6 on the foot plate I64. Sheaves 2I6, 22.6, 22I, 222, and 223 guide the cable'from the post 2I2 to the ring 2I1.

In operation, the stereoscope is adjusted in proper position with the winged mirrors 46 and 56 set parallel to and equidistant from their respective eye mirrors 26 and 26 directly over the phototables 66 and 16, the visual distances of each eye of the operator to the respective centers ofthe phototables being equal while the phototables are in a level position. These mirror adjustments are made possible by virtue of the fact that the wing mirrors are movable laterally along the bar 66 and tiitable in two directions on the angle brackets 55 and 56. The phototables are adjusted by turning the knobs III, 6|, and I25 for tilt, tip and elevation and by changing the position of the plates II6 between the guides I26 and I 21.

The plane surfaces I66 and I66 are then lev eled in the same horizontal plane normal to the visual axes of the stereoscope by means of the levelling screws. I66, I64, and I65, and I66, I61,- and I66. The columns I65 and I66 are then made perpendicular to the plane surfaces I66 and I66 by adjusting the posts I66 and I81. By these adjustments, the index marks I46 and I46 are made to move precisely vertical and parallel to the visual axes of the stereoscope when the bar I62 is moved on columns I65 and I66.

The map table I62 is then leveled and a pair stereoscopic photographs are mounted, each map table I32.

, This completes the reliminary adjustments of the instrument for making either a planimetric a map or a contour map.

To use theinstrument for making planimetric maps, the phototables 99 and III are held level and the index marks I48 and I49 are aligned so that each is viewed through the stereoscope over the center of its corresponding phototable. In accomplishing this, only one eye is used at a time so that the index marks will not appear stereoscopically. Then, one of the index marks, for example, index mark I48, is moved toward the other index mark I49 on the bar I62 to a point between the center of phototable 69 and the side thereof adjacent the map table I32 until both marks appear when viewed through the stereoscope with both eyes either to fuse or to be in alignment in the direction normal to the line of centers of the photographs.

If the marks do not appear to be sharply fused, that is, if they appear to be blurred, then the phototable 99 is turned or swung by rotating the knob 90 until the index marks appear fused and sharply deflned the while maintaining the stereoscopic overlap of the two photographs in clear relief as a spatial model. This is possible because, due to the tolerance of the eyes, stereoscopic pictures need only be brought into an approximate optimum position for seeing a sharply defined relief or spatial model. This fused image is commonly referred to as the floating mark. In this position the floating mark may appear to be displaced either above or below the surface of the spatial model at that point.

In this position, the index mark I49 is directly over the center of the photograph on the phototable and the index mark I48 is directly over the same object as it is represented in the photograph on the phototable 69. In this position, the floating mark may appear to be displaced either above or below the surface of the spatial model at that point. This displacement is then eliminated by elevating or as the case may be, until the floating mark appears to be in contact with the surface of the model at that point.

Then the index marks I48 and I49 are moved ,in unison laterally in the direction of the phototable 99 and up or down on the columns I65 and I66 until the floating mark, which will become blurred, appears approximately to contact the surface of the model at the center or at a well defined image point near the center of the photograph on the phototable 99. Then the other phototable 10 is turned until the floating mark again appears sharply defined through the stereoscope.

The map can be made on any chosen scale by changing the height setting of the index marks I48 and I49 and readjusting their spread to correspond with the change in height. The higher the index marks for a given setting, the smaller the scale. A higher position of the floating mark lowering the bar I92,

,where the floating mark requires that the index marks be spread farther apart to bring the floating mark in contact with the surface of the model at any given point.

The instrument is now adjusted for making the planimetric map. The floating mark carriage is moved overvthe plane surfaces I99 and I" to appears to contact the surface of the model at a point onlthe extreme end of a planimetri line, say a drainage line, and ring 2" is released from the pin III to permit the tracing point to contact the map table. Then, the carriage is moved so that the floating mark follows the selected planimetric line of the model,-

the while continually changin the elevation of the floating mark by turning the hand wheel I12 to cause the floating mark to appear to contact the surface of the model at every point along the planimetric line traversed.

When this traverse is completed, the tracing point is elevated by pulling the ring 2" and another planimetric line is selected for which the same procedure is followed. This is repeated for every desired planimetric line of the model until the map is completed.

To use the instrument for making topographic or contour maps, the same preliminary adjustments are made as described above. The photographs are then adjusted in correspondence relative to each other in the usual manner'by swinging, tipping, and tilting the phototables with the knobs 90, I25, and H3. In this position the spatial model may not .be in the true horizontal position, i. e., the model may be tilted or tipped so that the contours thereof are not truly horizontal. It is, therefore, necessary to horizontalize the model and thus to bring it in absolute orientation, while making any minor adjustments necessary to retain relative correspondence. The method of horizontalizing a spatial model by the use of basic reference points is well known to the art and is described in numerous works. See Photogrammetry News Letter, No. 3, volume 2 of 1936 and Ernfuhrung in die Luft-und Erdbildmessung" by K. Schwidefsky, pps. 82 to 86, which discuss the major operation of bringing photographs into relative orientation.

The instrument is now set for making the contour map. The height of the index marks I48 and I49 is set so that the floating mark appears to contact the model at a point whose elevation is the same as the elevation at which a contour line is desired and the tracing point 2 I3 is lowered in contact with the map table I32. Then the carriage is moved so that the floating mark at the height setting of the index marks appears constantly to contact the model at each change of position. In this manner the carriage follows the line of constant elevation. This movement is transmitted to the tracing point 2I3 which traces out the form line on the map table. When one contour line has been mapped, the height setting of the floating mark is changed by raising or lowering the bar I62 to the next contour elevation desired and the procedure repeated. This is done for each desired contour.

The present invention differs in principle from prior devices of a similar character employing two index marks in that these marks are vertically movable. This permits placing the floating mark in contact with different points on the model without spreading the index marks on the instrument. By holding the distance between the index marks constant and only changing their elevation, the map produced is on a uniform scale because the scale of the vertical pictures is larger with increased height of ground in inverse proportion. This is not true in the case of instruments where the index marks are held at a constant elevation and only a variation in their spread is possible, in which case there can be reproduced only a map having the same scale variation as the stereoscopic pictures. A higher setting of the index marks just compensates for an increased picture scale and, conversely, a lower settingjust compensates for a decreased picture scale. To illustrate this point, if the index marks were in contact with the photographs, a contour line would be traced out on the scale of the photographs' Since the photograph shows the objects in different scales at difierent elevations, the map would likewise show the same scale variations. However, if the index marks are elevated so that the floating mark coincides with a right section of the cone of rays of a particular object of the model, the scale will be reduced proportionately as the altitude of the cone of rays is to the altitude of the section. This proportion is exactly inverse to the proportion of the scales of the photographs at the corresponding elevations.

As stated differently, the model is always on a uniform vertical scale regardless of how much it is stretched, and, since the operator can make the floating mark contact the model at any point by simply raising and lowering the index marks, the contours drawn at every elevation will be on a uniform scale.

By making the eye distance from the stereoscope to the phototables greater than the focal length of the stereoscopic pictures to be viewed, a greater vertical mapping range is obtained than if the eye distance were equal to or less than this focal distance, although the model will appear to be vertically stretched. The greater the distance of the eye position, the greater is the vertical mapping range and this distance should preferably be large enough to permit operations on the highest altitude differentials to be encountered.

Having thus described my invention, I claim:

1. In a plotting instrument of the character described having a stereoscope, tables for supporting stereoscopic pictures and reference marks between and independent of said stereoscope and said tables, said marks being movable in three coordinate directions, a carriage supporting said 4 marks in spaced relation, and a mechanism con-. straining said carriage to move so that every,

position of said marks is parallel to every other position, said carriage having a stylus attached thereto in cooperative relation with a mapping surface.

2. In a plotting instrument of the character described having a stereoscope, tables for supporting stereoscopic pictures, transparent discs, and

index marks on said discs in a vertical plane between said stereoscope and said table, frames for mounting said discs, vertical arms secured to said frames, a horizontal bar, sleeves slidable on said bar, one for each index mark, said arms bein vertically slidable on said sleeves, vertical posts at the ends of said bar, means for slidably supporting said bar on said posts, means for vertically moving said bar on said posts, means for holding said bar in different positions along said posts, a rod secured to said posts, a stylus secured to said bar, a'mapping surface in cooperative relation with said stylus, and means constraining the movements of said posts and rod horizontally and co-directionally.

B. In a plotting device having means for mount- 75 ing stereoscopic pictures, a stereoscope for viewing said pictures, a pair of reference marks between said mounting means and said stereoscope, a mapping surface and a stylus; a carriage for supporting said marks in the field of view of the stereoscope, said carriage being movable in a plane normal to the visual axes of the stereoscope, means for moving said marks on said carriage parallel to said visual axis, and means constraining said carriage tomove so that every position of said marks is parallel to every other position, said stylus being attached to said carriage for tracing lines on said mapping surface in accordance with the movements of said carriage.

4. In a plotting device having means for mounting stereoscopic pictures. a stereoscope for viewing said pictures, a mappin surface, a stylus and a pair of spaced reference marks between said mounting means and said stereoscope: said stereoscope being vertically over said mounting means, a carriage for supporting said marks in the field of view of the stereoscope, said carriage being movable in a horizontal plane, means for moving said marks vertically on said carriage, and means constraining said carriage to move so that every position of said marks is parallel to every other position, said stylus being attached to said carriage for tracing lines on said mapping surface in accordance with the movements of said carriage.

5. In a plotting device having means for mounting stereoscopic pictures, a stereoscope for viewing said pictures, a pair of spaced reference marks between said stereoscope and said mounting means, a mapping surface and a stylus; said stereoscope being vertically over said mounting means, means for changing the spaced relation of said marks, a carriage for supporting said marks in the field of view of the stereoscope, said carriage being movable horizontally, means for moving said marks vertically on said carriage, and means constraining said carriage to move so that every position of said marks is parallel to every other position. said mapping surface being fixed relative to said carriage. said stylus being attached to said carriage for tracing lines on said surface in accordance with the movements of said carriage.

6. In a plotting device having tables for mounting stereoscopic pictures, a stereoscope for viewing said pictures, a pair of reference marks between said tables and said stereoscope, a mapping surface, and a stylus; means for tipping and tilting each table about a point above its plane, means for swinging each table about a center point thereof, said stereoscope being vertically over said tables, a carriage supporting said marks in the field of view of the stereoscope, said carriage being movable horizontally, means for moving said marks vertically on said carriage, and means constraining said carriage to move so that every position of said marks is parallel to every other position, said mapping surface being fixed relative to said carriage, said stylus being attached to said carriage for tracing lines on said surface in accordance with the movements of said carriage.

7. In a plotting device having means for mounting-stereoscopic pictures, a stereoscope for viewing said pictures, a pair of spaced reference marks between said mounting means and said stereoscope, a mapping surface. and a stylus; a carriage supporting said marks in the field of view of the stereoscope, said carriage being movable horizontally, means for moving said marks vertically on said carriage, means constraining said said surface.

earrialetomovesothatevewpositionotsaid marks is parallel to every other position. means adjustabiy supportinssaid mappinfl surface, said stylus beins attached to said earriazefor train: lines on. said surface in accordance with the movement or said carriaze, and means for raising and lower-in: said stylus in and out or contact with 8. In a stereoscnpic plotting device havin:

reference marks. transpare t discs, said reference marks'beinlinseribedonsaiddiscabraekets !or bar for supportinl said supnortins' said discs. a

bmketn said brackets beinl movable on said bar.

,a frame for horizontally mpmrtins said bar, and

means (or vertically muvinl said bar on said frame. 

